Heat Exchanger Hook-up

[Tim Crowley]

Folks, I've been operating my eclassic for about 5 months now, but it's being tested in Vermont temps. now.  Wanted to ask this question:  I've got a 50 plate heat exchanger into the bottom of which my line-in is connected.  Said another way, the water from the outside boiler is connected to the bottom of the heat exchanger, then comes out the top.  Is that the right hook-up, or am I missing something?  I've read a thread on this on the forum, but I can't seem to find it.  Thoughts?  Tim

[beenthere]

Seems the hot from the boiler would come in the top of the HE and the cooled water would exit the bottom.
Edit:  Upon closer look at the link I see that the hot water supply does come in at the bottom of the HE and returns out the top. So Tim, agree yours is right. Sorry for the confusion I added. 

When heating the water like in the wood fired boiler, the cold would come in the bottom and the hot out the top.

The house loop (if hydronic), the return water would come to the heat exchanger at the bottom and the warmer water out the top.
Make sense?

This was discussed recently (haven't found the thread) and the thought was along these lines. There were pics or drawings of how it should be.

This one might help.
http://www.centralboiler.com/forcedAirDet.html

[Tim Crowley]

Thanks, beenthere.  Could someone help us find that thread/post as I'd like to get this corrected if it's not hooked-up right.  I just want to make sure I'm maximizing the boiler's potential and not selling its ability short for something like that.  The eclassic is serving a System 2000 boiler that provides hot air to half the house and baseboard to the other half (large old farmhouse).  What I'm finding is that the heat exchanger in the plenum "takes" the majority of the heat from the OB's water, leaving water that's not the 180 degrees that the baseboard needs to function at its best.  Does this make sense?  When I turn off the air heat, the temp. in the System 2000 boiler rises, thus serving the baseboard the temps it needs.  Hmmm . . .
Tim

[Jeff]

A quick call to central boiler might be your best bet.

[red oaks lumber]

you need a bigger circulating pump, water is moving to slow allowing the h.ec. to blow off to much heat as it goes thru , that is a good problem to have

[Tim Crowley]

Interesting "problem" to have, huh.  When the hot air side stops calling and the fan shuts off, etc, then the inside boiler temp. goes to max (180+) from 140.  Then, the baseboard seems to have enough to do what IT was designed to do, radiate the heat.  Are you suggesting that the water that's circulating to the plenum in the hot air part of the furnace is moving too slow?

Tim

[irallen]

You have the correct hookup.

[Tim Crowley]

Irallen, when you say I have the correct hook-up, are you saying that the water line from the boiler should be hooked-up to the bottom of the heat exchanger?

Tim

[SPIKER]

you want to make sure that any AIR that is trapped can leave the heat exchanger, that means the EXIT should be at the top so no bubble can form/set.   If you plumb water in at the top the air an become un-entrapped in the exchanger and steam / air will not be able to get out leaving bubbling sounds coming from it...

You can set the baseboard heaters to take heat first? feed them then the furnace air circulatory?   This would make sure you have HOT water at the baseboards and that also means when they are all on and pulling hot water the heat exchanger in the air duct will not have as much HEAT available (if you are firing the air mover/furnace up or down stream in extreme conditions the cooler water will draw heat out of it unless the heat exchanger is in the return ducting...


Mark

[Tim Crowley]

Mark,

Wow!!  I was actually wondering about that possibility (giving the baseboard the hottest water first)!!  Didn't think it was possible.  What (generally) does that involve?  Is it a valve of some sort, replumbing in a major or minor way?  Some simple or complicated redirection?  My plumber did say a couple of weeks ago when I was concerned about the baseboard not gaining the heat it should, that, by all accounts, the heat exhanger for the air system was "certainly doing its job taking all the heat it could from the OB water."  He did check for air in the baseboard system, just to be sure.  None there, really.  He suggested running a couple of flexible ducts to that main living room to "assist" the baseboard.  But I got to thinking, now that the temps. are giving me a truer picture of things, that one half of the system was certainly robbing the other, it seemed.  Tell me more!!  Tell me more!!

Thanks, Mark.   

[woodmills1]

I wonder if you put the baseboard first will they rob enough heat so that the air will be too cool?

[beenthere]

Here is the thread
http://www.forestryforum.com/board/index.php/topic,40218.msg584889.html#msg584889

[red oaks lumber]

put in a bigger pump, no need to replumb everything. if your water temp coming back out of the heatechanger is cool to the touch put in a bigger pump(more g.p.m.) horizontal heat ec. infeed line on the bottom return line on top..... need more heat use a bigger pump, your not airlocked if your getting heat the problem is ... get a bigger pump
 been there done that!!

[red oaks lumber]

here is an idea.. put in a bigger pump

[maple flats]

Not sure about the hookup on that but when I sold and installed similar untis often times more than 1 zone was called for. This can be done a couple of different ways. You will need a thermostat for each zone. You can split the flow in a manifold and have a pump for each or you can use 1 pump and zone valves. You will need check valves to make sure the hot water comes from the boiler and not back fed from another zone. Either way will give you fully hot water to each. You may need a bigger pump if the flow is not great enough because you likely don't want to add a new line from the boiler. Even a 3/4" line with a higher flow pump will move a lot of BTU's, 1" is even better. If you just go through the baseboards first you may starve the heat exchanger for needed BTU's and will get cool drafts in the house.

[Tim Crowley]

Thanks everyone.  These answers certainly help my conversations with my plumbers.  They're good guys, and they know what they're doing, but every system is different, so I like to at least ask them intelligent questions.  I think it makes me and them a little smarter about my particular system.  Of course, OWB's are not their specialty, so I like to make sure they're not making any wrong assumptions, etc.  It does seem to me that my goal should be to send 180 degree water to EACH system (baseboard and hot air), but the fact that they share the same boiler may make that impossible?

Thanks again.  I could NEVER have gotten this far with my OWB system without you guys. 

Tim

[Tim Crowley]

Hey Beenthere:  I just noticed your edit.  Thanks. When I looked at the diagram, I couldn't really tell, so thanks for taking another look!

Tim

[ken999]

Just a thought here...

Assuming your baseboard works best at 180, shouldn't you try sending water from the OWB to the exchanger at a HIGHER temp? You will loose some heat in the exchange, so it would seem logical to increase OWB temp until you get the correct temp on the 'house side'?

I'm not saying this is the overall solution to the problem, just something to think about/wondering out loud...

[SPIKER]

Just a thought here...

Assuming your baseboard works best at 180, shouldn't you try sending water from the OWB to the exchanger at a HIGHER temp? You will loose some heat in the exchange, so it would seem logical to increase OWB temp until you get the correct temp on the 'house side'?

Ken: 180 is pretty warm, much more and a chance of a boil over or simply wasting wood is increased a LOT.   

Flow rate will only help some, the water has to stay in long enough to actually pass the heat to the rest of the system.   There is a calculation for heat exchangers that tells you how long the air has to stay in the exchanger to pick up the heat form the water.   while the higher the temp is the less time it needs to be in the exchanger.   You need to know Airflow, Water flow and inlet & outlet temps of both water & air.    (Cant remember if this was over a water to air exchanger or water to water?) prior to the room baseboards.?

In either way the baseboards will need the higher temp water as the water to air heat transfer is much less than what it is for the heat exchanger be it water to water or water to air as the heat exchanger has forced heat transfer dynamics.    The baseboard units if not powered are depending on convection heating to pull cool air in at bottom and warm air out the top...

Mark

[ken999]

Spiker- CB recommends running the e-Classics at 185 and the controller (at least mine) will not go above 195. If I wanted 180 on the house side of the plate exchanger, I'd try 185 at least.

Certainly getting the heat to the baseboard FIRST will help, if those zones are priority.

[SPIKER]

Spiker- CB recommends running the e-Classics at 185 and the controller (at least mine) will not go above 195. If I wanted 180 on the house side of the plate exchanger, I'd try 185 at least.

Certainly getting the heat to the baseboard FIRST will help, if those zones are priority.

That might be:  Is the E-Classic a closed loop pressurized slightly or open to atmosphere?   This would make a big difference as water at 180+ exposed to atmosphere evaporates very quickly especially in winter low moisture cold temps...   Boiling Pot idea, put a lid on it and it will boil at higher temp and less heat input with less BTU lost due to steam/off gassing (Heating water, 1BTU required to raise 1 gallon of water up 1 degree F.)   now let the heat escape in form of steam you see that you are loosing those BTUs and will use more wood, to heat up the cold incoming water (replacing what evaporated) and the cooling effect on the rest of the remaining water when the water turns to steam/gas.   While you do not need to actually make "Steam" to loose a good bit of water to evaporation when the water is heated up.
You dont have to maintain much in the way of back pressure either to increase the heat holding ability of the water without it turning to steam/evaporating.  every couple PSI equals several degrees higher in water temp ill it actually turns to steam.   Altitude also will play some part, some one in Denver at 1 mile above sea level will loose more water at the same temp vs someone at sea level due to decreased pressure.

Mark

[red oaks lumber]

i would spend $100 on a bigger pump, that is the easiest way to fix the problem and, if by chance it doesn't help atleast you have a spare pump.

[ken999]

Thanks Mark. I hadn't thought of that. That must be why CB only allows the controller to top out at 195. I'm not sure if the vent cap constitutes a 'lid', but the system is referred to as an unpressurized.